Variable Speed of Light Cosmology and Bimetric Gravity: An Alternative to Standard Inflation

Moffat, J. W.

doi:10.1142/9789812701992_0024

Cited by 10 publications

(16 citation statements)

References 15 publications

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“…The length scale (∆x total ) min (l 2 Pl l dS ) 1/3 therefore corresponds to at least three interesting physical scenarios. It may be interpreted as (i) the classical radius of a 'particle' with both minimum energy and minimum energy density, (ii) the classical radius of a 'particle' with both maximum energy and maximum energy density, and (iii) the classical radius/minimum total uncertainty of the electron, which saturates the charged particle stability bound (44). In the context of the DE-UP model [19,20], all three interpretations satisfy the general holographic relation, Eq.…”

Section: A Holographymentioning

confidence: 99%

“…Particular classes of models, in which the variation of physical constants should, automatically, imply a modification of the DE-UP formulae, Eqs. (40) and (41)- (42), include those with a running gravitational coupling [37][38][39][40], variable speed of light [41][42][43][44][45][46][47][48], or dynamical dark energy field [49][50][51][52]. (See also [53][54][55][56][57] for current bounds on varying α e theories, including their effects on cosmic string phenomenology [58,59] and [60][61][62][63][64] for more general models involving variations of multiple physical constants.…”

Section: Additional Cosmological Implicationsmentioning

confidence: 99%

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Is there a connection between “dark” and “light” physics?

Lake

2017

J. Phys.: Conf. Ser.

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In the early-mid 20 th century Dirac and Zel'dovich were among the first scientists to suggest an intimate connection between cosmology and atomic physics. Though a revolutionary proposal for its time, Dirac's Large Number Hypothesis (1937) adopted a standard assumption of the day, namely, the non-existence of the cosmological constant term (Λ = 0). As a result, its implementation necessitated extreme violence to the theory of general relativity -something few physicists were prepared to sacrifice in favour of 'numerology' -requiring a time-dependent gravitational coupling of the form G(t) ∼ 1/t. Zel'dovich's insight (1968) was to realise that a small but nonzero cosmological term (Λ > 0) allowed the present day radius of the Universe to be identified with the de Sitter radius, rU l dS 1/ √ Λ, which removed the need for time-dependence in the fundamental couplings. Thus, he obtained the formula Λ m 6 G 2 / 4 , where m is a mass scale characterising the relative strengths of the gravitational and electromagnetic interactions, which he identified with the proton mass mp. In this paper, we review a number of recent arguments which, instead, suggest the identification m = me/αe, where me is the electron mass and αe = e 2 / c 1/137 is the usual fine structure constant. We note that these are of a physical nature and, therefore, represent an attempt to lift previous argumentsà la Dirac from the realm of numerology into the realm of empirical science. If valid, such arguments suggest an intimate connection, not only between the macroscopic and microscopic worlds, but, perhaps even more surprisingly, between the very essence of "dark" and "light" physics.

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Section: A Holographymentioning

confidence: 99%

Section: Additional Cosmological Implicationsmentioning

confidence: 99%

Is there a connection between “dark” and “light” physics?

Lake

2017

J. Phys.: Conf. Ser.

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“…VSL models are a popular alternative to inflation which may be physically realised, for example, in disformally related bimetric theories, which allow the ratio of the speed of light to the speed of gravity to vary [36][37][38]. Proponents argue that it is more predictive than inflation, and does not suffer from problems of fine-tuning present in inflation [39].…”

Section: Variable Speed-of-light Cosmologymentioning

confidence: 99%

“…Proponents argue that it is more predictive than inflation, and does not suffer from problems of fine-tuning present in inflation [39]. While here we are interested in the early universe effects of a variable speed of light, constraints on and evidence for VSL cosmologies at late times [40,41] have also been studied.…”

Section: Variable Speed-of-light Cosmologymentioning

confidence: 99%

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Non-Standard Hierarchies of the Runnings of the Spectral Index in Inﬂation

Longden

2017

Universe

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Recent analyses of cosmic microwave background surveys have revealed hints that there may be a non-trivial running of the running of the spectral index. If future experiments were to confirm these hints, it would prove a powerful discriminator of inflationary models, ruling out simple single field models. We discuss how isocurvature perturbations in multi-field models can be invoked to generate large runnings in a non-standard hierarchy, and find that a minimal model capable of practically realising this would be a two-field model with a non-canonical kinetic structure. We also consider alternative scenarios such as variable speed-of-light models and canonical quantum gravity effects and their implications for runnings of the spectral index.

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Spontaneous Lorentz breaking at high energies

Cheng

Luty

Mukohyama

et al. 2006

J. High Energy Phys.

113

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Theories that spontaneously break Lorentz invariance also violate diffeomorphism symmetries, implying the existence of extra degrees of freedom and modifications of gravity. In the minimal model ("ghost condensation") with only a single extra degree of freedom at low energies, the scale of Lorentz violation cannot be larger than about M ∼ 100 GeV due to an infrared instability in the gravity sector. We show that Lorentz symmetry can be broken at much higher scales in a non-minimal theory with additional degrees of freedom, in particular if Lorentz symmetry is broken by the vacuum expectation value of a vector field. This theory can be constructed by gauging ghost condensation, giving a systematic effective field theory description that allows us to estimate the size of all physical effects. We show that nonlinear effects become important for gravitational fields with strength √ Φ > ∼ g, where g is the gauge coupling, and we argue that the nonlinear dynamics is free from singularities. We then analyze the phenomenology of the model, including nonlinear dynamics and velocity-dependent effects. The strongest bounds on the gravitational sector come from either black hole accretion or direction-dependent gravitational forces, and imply that the scale of spontaneous Lorentz breaking is M < ∼ Min(10 12 GeV, g 2 10 15 GeV). If the Lorentz breaking sector couples directly to matter, there is a spin-dependent inverse-square law force, which has a different angular dependence from the force mediated by the ghost condensate, providing a distinctive signature for this class of models.

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Variable Speed of Light Cosmology and Bimetric Gravity: An Alternative to Standard Inflation

Cited by 10 publications

References 15 publications

Is there a connection between “dark” and “light” physics?

Is there a connection between “dark” and “light” physics?

Non-Standard Hierarchies of the Runnings of the Spectral Index in Inﬂation

Spontaneous Lorentz breaking at high energies

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